As existing oil fields in shallow water environments become depleted, exploration and oil field development in deep water areas is becoming more common. However, these deep water areas provide challenges and the operating costs and time to perform operations are far greater than in the traditional shallow water environments. One example of this is the deployment and installation of subsea production trees. In relatively shallow environments a tree can be installed relatively quickly, however, in deep water environments, for example 1500 meters, operational time is greatly increased. As drilling rigs which are capable of operating at this depth cost in the order of $750,000 per day it is desirable to minimise the time for which the rig is required.
Traditionally, completion and tree deployment have been conducted as a single phase operation, however, this leads to the drilling schedule being dependent upon the tree delivery schedule. In order to mitigate this dependence between tree delivery and drilling programme, “batch” drilling and completion operations are undertaken followed by a programme of “batch” tree deployment and well clean up operations. Once the drilling and completion operations are finished the well is suspended by a plug which seals the well bore. When the tree deployment and well clean up operations take place the tree is installed and integrity tested, and the plug is removed.
Batch operating, however, can lead to a considerable period of time elapsing between well completions and clean up operations. Although this increases the efficiency of rig operations, it can have a detrimental effect on well productivity.